ANSI - American National Standards Institute
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Clocks Roll Back on October 31 as "Standard" Time Begins Again

New York, Oct 29, 2004

An extra hour of "snooze time" is in store for most Americans on Sunday, October 31, when (with only a few exceptions) clocks across the U.S. "fall back" to Standard Time at 1:59 a.m. and 2004 Daylight Saving Time (DST)1 officially ends.

Like all successful standardization activities, government, industry and the general public have worked together to create today's accepted standards for time. Propelled in large part by the railroad industry and its concern about the inconsistencies of local mean time, in the 1840's Britain became the first country to formally establish a standard for time throughout a region. Standard time in time zones was instituted in the U.S. and Canada by the railroads on November 18, 1883. Before then, time of day was a local matter, and most cities and towns used some form of local solar time, maintained by some well-known clock (e.g., on a church steeple or in a jeweler's window.)

The concept of daylight saving time (sometimes referred to as "Sun Time" or "Summer Time") can be traced back to Benjamin Franklin (circa 1784). However, Franklin's concept was never fully advocated or seriously considered until World War I when nations began concentrated efforts to conserve fuel needed to produce electric power. [Present day studies indicate that Daylight Saving Time actually trims U.S electricity usage by nearly one percent (1%) each day DST is in effect, with peak savings of up to 5% in the first week of implementation.]

The first nationwide U.S. effort to preserve daylight and provide standard time was unsuccessful. A 1918 law was repealed within one year, though it became a local option and was continued in a few states and certain metropolitan areas. Ongoing discussions about the use of a single time standard for the U.S. ultimately culminated in the approval of the Uniform Time Act of 1966. The Act was able to eliminate the use of local laws and customs and establish a single pattern for Daylight Saving Time throughout the U.S., exempting only those states that passed a state law (currently, this list includes parts of Indiana and Arizona, the state of Hawaii and the U.S. territories).

DST begins for most of the United States on the first Sunday of April and reverts back to Standard Time on the last Sunday of October. The 2:00 a.m. changeover time was selected for its practicality factor and to minimize disruption (i.e., it is early enough so that the entire U.S. has switched by daybreak and late enough to prevent today switching back to yesterday); each time zone switches at the appropriate time.

Given the direct linkage of the new time system with the railroad industry, the Interstate Commerce Commission, which in 1918 was the only federal transportation regulatory agency, was first assigned the role of the nation's timekeeper and given responsibility to make any changes to time zones. When Congress created the Department of Transportation in 1966, it transferred the responsibility for the time laws to the new department.

Keeping Track of Time

While responsibility for time zone management lies with the Transportation Department, the United States Naval Observatory (USNO), whose primary functions are to provide time for navigation and military purposes, and the National Institute of Standards and Technology (NIST), the country's national metrology institute and an ANSI member, cooperatively act as the country's official sources of time.

A non-regulatory federal agency within the U.S. Commerce Department's Technology Administration, NIST also helps to define the official world time (known as "Coordinated Universal Time, or 'UTC'"), with the most accurate clock in the world. A cesium atomic clock located at NIST's Boulder, Colorado laboratories, this non-traditional timepiece is known as NIST-F1 and uses lasers, sophisticated tracking devices and cesium atoms to identify the characteristics that define the unit of time known as a "second."

Introduced in late 1999, NIST-F1 is believed to be so precise that it will neither gain nor lose a second in nearly 20 million years. It is considered the official clock of the U.S. and is part of an international network of the world's atomic clocks that is used to define UTC.

1 Note that the correct spelling is Daylight "Saving" (not "Savings") Time.

This article was originally published by ANSI in October 2002.